In the dairy-based confection industry, the trend towards continuous processing has followed two routes, one using high efficiency heat exchangers and the other creating a continuous version of traditional processes using cookers equipped with mechanical scraping means. The latter (mechanical scraping) gained ascendancy in the dairy-based confection industry due to its ability to run continuously without cleaning for prolonged periods of time, such as several days. In the case of high efficiency heat exchangers, the proteins in dairy components tend to precipitate out fairly rapidly and foul heat transfer surfaces thereby necessitating chemical cleaning of the heat exchangers roughly every 6 to 12 hours depending upon protein content of the feed slurry. Regarding dairy cookers, the trends which have attempted to automate cooking processes using them have added more machinery and more moving parts, thereby resulting in increased plant space costs, plant investment costs, machinery maintenance costs and power costs to produce confections. See Sugar Confectionery Manufacture, Second Edition, E. B. Jackson Ed., Chapman & Hall, Glasgow, 1995, pp. 176-182.
In the manufacture of confections, it is known to decrease processing time by admitting steam directly into a pre-mixed mass used for making a confection so as to more rapidly heat the same and cook the ingredients to obtain the desired confectionery. As disclosed in U.S. Pat. No. 4,056,640 to Otto, this method allows the artisan to minimize the added water content in the confectionery pre-mix and thereby reduce product cooking times. However, in this method the pre-mix contains dairy or protein components which are heated in a conventional cooker having a plurality of moving parts, including paddles, for mixing the confectionery mass. Accordingly, while direct steam heating and cooking may shorten the actual processing time necessary to make a confectionery product, the numerous moving parts in a conventional cooker require great labor and expense to maintain and clean. In addition, the extended cook times involved in using conventional cookers tend to burn protein components, cause product discoloration via the Maillard reaction which results in caramel off-notes, and foul the cookers with protein precipitates and caking.
Significant reductions in cook time for making a confection have been realized through the use of high efficiency heat exchangers such as wiped film or scraped surface cookers. However, wiped film or scraped surface heat exchangers have numerous moving parts, thereby requiring extensive labor costs for cleaning and maintenance and are considerably more expensive. Moreover, adding elements to create turbulence creates dead spots in heat exchangers, thereby burning the confectionery mass and further complicating the task of cleaning the heat exchanger. As a result, while scraped surface heat exchangers have been utilized for dairy-based confections, their high initial capital investment, and clean up and maintenance costs have limited their wide-spread appeal in dairy-based confection applications.
Regardless of the processing apparatus used, a further problem encountered with temperature sensitive candy masses, such as those containing dairy or protein components, is the burning, denaturing or precipitation of the protein at the beginning of the process or in the beginning of the production line. Such burning and precipitation of protein depends upon the milk composition, the proportion of milk in the total candy mass and the actual temperature level to which the mass is exposed. In an attempt to solve this problem, U.S. Pat. No. 5,298,266 to Mergelsberg et al discloses pre-heating a dairy or protein containing candy stock in a mixing head by direct steam injection prior to feeding the stock into a coiled heat exchanger which contains no moving parts. However, injecting steam into a culinary product requires food grade steam and when it condenses additional energy is needed to remove the added water.
Recently, plate and frame heat exchangers have been proposed as a way of further minimizing the cooked time needed to develop sugar in a heat-sensitive candy mass, such as one containing a dairy component or a protein component. Plate and frame heat exchangers are gaining prominence in the confection industry, most notably commercially via Ruffinatti, replacing coil based cookers for production of non-dairy based confection products, such as chews or high-boiled sweets. They have even been utilized for dairy-based confections but have been limited to six to twelve hour run times because the protein tends to denature, precipitate out and foul the heat transfer surface on the plates, thereby necessitating chemical cleaning wash-outs. This has limited their acceptance for use in dairy-based confection applications due to the short run times in relation to the long, two hour or more, clean-up times. Accordingly, mechanically scraped surface type heat exchangers and cookers remain the most popular mode for dairy-based applications.
The present invention provides a method for making dairy-based or protein containing cooked confections, such as chewy candies or hard candies, while at least substantially or completely avoiding the burning, precipitation and fouling problems associated with heating a confectionery mass in the presence of a dairy component or a protein component. At the same time an efficient process is provided which reduces processing times and saves on energy, maintenance, plant and equipment costs. Flavor development and a whiter product may be achieved without caramel off-notes using a very quick cook and minimal protein exposure to high temperatures in accordance with the method of the present invention. Accordingly, the present inventors have found a continuous process of making a dairy-based or protein containing confection which reduces cooking time, as well as costs associated with maintenance, clean-up and space requirements, and at least substantially or completely avoids protein burning and precipitation problems over prolonged periods of operation, such as at least about 24 hours. In addition, the present invention provides an apparatus for carrying out the method of the present invention which employs static mixing thereby reducing maintenance costs and energy costs for motors, scrapers, and other moving parts. The apparatus also provides a large heat transfer area for cooking thereby permitting the use of lower steam pressures to obtain a given cook temperature.